Upload & Sell: On
The rest of the story. Moved the drobo-s and connected it to the iMac using the dongle above. Drobo dashboard on iMac does not see it. Reconnected via USB 2 and the dashboard now see's it. Formated to HFS+. Tested write speeds and got an underwhelming 33MB/sec - geez! Shut it down, reconnected via the dongle and unlike the windows machine, the dashboard still does not see it BUT, the iMac does!. Tested write speeds, now getting approx 85MB/sec. Not quite 3 times faster but close enough. Setup and pointed Time machine to a sparsebundle on the drobo-s and its currently doing its thing.
So what has this done?
1. My old drobo-s (ver 1) that does not have USB 3 is now working with the iMac which does not support eSata but via the dongle is working at USB 3.0 speeds which are close to eSata.
2. Yet to be determined, if operating this unit without the dashboard has complications on the iMac
3. My Drobo 5D thunderbolt is free for managing photos, etc...